1. Field of the Invention
The present invention relates to an electric apparatus configured to cool a cooled part by using a centrifugal fan.
2. Description of the Related Art
For size reduction and silent driving, some electric apparatuses use air drawn by a centrifugal fan, such as a sirocco fan (which will be referred to a “sirocco fan” hereinafter) to cool a cooled part. See Japanese Laid-Open Nos. 2002-122839 and 2004-151648. The sirocco fan is a fan that draws the air as a result of an impeller rotates in the casing, and an air blowoff channel from the impeller is formed in the casing so that the blowoff channel can spread in the rotating direction of the impeller.
However, the sirocco fan has a drawing speed distribution on its drawing surface due to the above casing's structure. When there is maintained a sufficient distance between the cooled part and the drawing surface of the sirocco fan the drawing speed distribution is little influential, but as the electric apparatus becomes smaller the cooled part may often be located near the drawing surface.
Unless the drawing surface of the sirocco fan is properly arranged to the necessary cooling air amount of the cooled part by taking the above drawing speed distribution into consideration, the cooling efficiency lowers to the cooled part and as the number of fan's rotations increases the noise increases accordingly.
An airflow control member can be added near the drawing surface so that the cooling wind can efficiently flow around the cooled part, but its arrangement is difficult due to the space limitation and the noise can increase. Moreover, a similar problem occurs when a large cooling assistance member, such as a heat sink, is arranged near the drawing surface in order to increase the cooling efficiency.